class Square extends React.Component {
  render() {
    return (
      <button className="square"
        onClick={() => this.props.onClick()}>
        {this.props.value}
      </button>
    );
  }
}

class Board extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      squares: Array(9).fill(null),
      xIsNext: true
    };
  }

  handleClick(index) {
    const squares = this.state.squares.slice();
    squares[index] = this.state.xIsNext ? 'X' : 'O';
    this.setState({
      squares: squares,
      xIsNext: !this.state.xIsNext
    });
  }

  renderSquare(i) {
    return <Square value={this.state.squares[i]}
      onClick={() => this.handleClick(i)} />;
  }

  render() {
    const status = `Next player: ${this.state.xIsNext ? 'X' : 'O'}`;

    return (
      <div>
        <div className="status">{status}</div>
        <div className="board-row">
          {this.renderSquare(0)}
          {this.renderSquare(1)}
          {this.renderSquare(2)}
        </div>
        <div className="board-row">
          {this.renderSquare(3)}
          {this.renderSquare(4)}
          {this.renderSquare(5)}
        </div>
        <div className="board-row">
          {this.renderSquare(6)}
          {this.renderSquare(7)}
          {this.renderSquare(8)}
        </div>
      </div>
    );
  }
}

class Game extends React.Component {
  render() {
    return (
      <div className="game">
        <div className="game-board">
          <Board />
        </div>
        <div className="game-info">
          <div>{/* status */}</div>
          <ol>{/* TODO */}</ol>
        </div>
      </div>
    );
  }
}

// ========================================

const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(<Game />);
